earliest periods, its history is extremely obscure.

Wheat is of two principal kinds, characterized as soft and hard wheat,
though there are hundreds of named varieties of the grain. The
distinction between many of these is due to variation in the relative
proportions of starch and nitrogenous matter. Some contain not more than
eight per cent of nitrogenous elements, while others contain eighteen or
twenty per cent, with a corresponding decrease in carbonaceous elements.
This difference depends upon the soil, cultivation, season, climate, and
other conditions under which the grain is produced.

The structure of the wheat grain consists of an external tegument of a
hard, woody nature, so coherent that it appears in the form of scales or
bran when the wheat is ground, and an inner portion, more soft and
friable, consisting of several cellular layers. The layer nearest the
outer husk contains vegetable fibrin and fatty matter. The second layer
is largely composed of gluten cells; while the center comprising the
bulk of the grain, is chiefly made up of starch granules with a small
proportion of gluten.

The structure of a wheat kernel is well illustrated in the are situated
in different parts of the grain, and not uniformly distributed
throughout its structure. The outer husk of the berry is composed wholly
of innutritious and indigestible matter, but the thin layers which lie
next this outer covering contain the larger proportion of the
nitrogenous elements to be found in the entire kernel. The central
portion consists almost wholly of farinaceous matter.

[Illustration: Sectional View of Wheat Kernel.]

Phosphates and other mineral matter are present to some extent
throughout the entire grain, but preponderates in the external part.
Here is also found a peculiar, soluble, active principle called
diastase, which possesses the power of converting starch into sugar. The
dark color and marked flavor of Graham bread is undoubtedly due to the
influence of this element.

Until within a few years the unground grain was rarely used as an
article of food, but people are beginning to appreciate its
wholesomeness, and cracked, rolled, and pearled wheats are coming
rapidly into favor. Cracked wheat is the grain cleaned and then cut into
two or more pieces; in rolled wheat the grains are mashed between
rollers, by which process they are thoroughly softened in every part,
and are then easily cooked. Pearl wheat is the whole grain